Lewis & Short

īle, is, and īlĕum, ei, and īlĭum, ii, n., usually plur. īlĭa, ĭum, n. (heterocl. dat. sing. ilio, in the pun with Ilio from Ilion, Poët. ap. Serv. Verg. A. 7, 499; dat. plur. iliis, Cels. 4, 1 fin.), that part of the abdomen which extends from the lowest ribs to the pubes, the groin, flank.

  1. I. Lit., Ov. M. 3, 216; 12, 486; Verg. G. 3, 507; id. A. 7, 499; Hor. Epod. 3, 4: ilium vitia, Plin. 20, 5, 15, § 31: ducere ilia, to draw the flanks together, become broken-winded, Hor. Ep. 1, 1, 9; so, trahere, Plin. 26, 6, 15, § 29: rumpere ilia, to burst, Verg. E. 7, 26.
  2. II. Transf., the entrails of animals, Hor. S. 2, 8, 30; Mart. 10, 45, 4, Juv. 5, 136.
    1. B. The belly or body of a vessel, Juvenc. 2, 141.
    2. C. Sing., the private parts, Cat. 63, 5.